Electric measuring instrument.



No. 678,236. Patented July 9, I901.

W. C. FISH.

ELEITTFIIC MEASURING INS TRUMENT.

(Application filed A 'r. 4, 1901.

(N0 llodel.)

J n m N) W lnvencor Walter C. F15 l'l M m: uonms PETER 00.. PHOYc-L THQ.wAsNmGYON. a. c.

UNITED STATES PATENT OFFICE.

WALTER C. FISH, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE GENERAL ELECTRICCOMPANY, OF NEW YORK.

ELECTRIC MEASURING INSTRUMENT.

SPECIFICATION formingpart of Letters Patent No. 678,236, dated July 9,1901. Application filed April 4, 1901- Serial N 0. 54,252. (No model.)

To all whom it may concern:

Be it known that I, WALTER O. FIsH, a

citizen of the United States, residing at Lynn,

county of Essex, State of Massachusetts, have invented certain new anduseful Improvements in Electric Measuring Instruments, (Case No. 1,621,)ofwhich the following is a specification.

Electric measuring instruments which employ iron or other magneticmaterial in their construction possess the important ad vantage of largedirective force, whereby the effect of friction of the moving partsbecomes insignificant. Such instruments may therefore be made simple andstrong Without introducing any perceptible error due to friction. Suchadvantages as these instruments may possess, however, arecounterbalanced by the serious error due to hysteresis of the ironforming part of their construction. This source of error generallycauses such instruments to read low upon rising current and high uponfalling current. This error I have discovered may be eliminated bysuperposing upon the iron of such an instrument an alternatingmagnetomotive force of proper frequency and value.

The accompanying drawing represents in diagram one embodiment of myinvention.

In the diagram I have represented a number of measuring instruments, inthis case of the direct-current type, in which the current to bemeasured passes through a solenoid, the magnetic field of which actsupon an iron rod or core suitably connected to a pointer, the deflectionof which represents in suitable units the current passing through thesolenoid. The instruments thus shown are sup posed to be mounted upon aswitchboard and connected, respectively, to various feeders or mainsleading from the station.

At 1 and 2 are indicated a pair of bus-bars from which extend any numberof sets of mains'-as, for example, the mains 3 4, 5 to 6, and 7 8. Eachof these pairs of mains feed any suitable translating devices,(indicated conventionally at 9, 10, and 11, re spectively.)

In order the better to represent the construc- 5o tion of ameasuring-instrument of the character described, I have at 12 shown suchan instrument partly in cross-section.

At 13 is shown a coil in series with the main 4, which,in conjunctionwith the main 3, feeds the translating devices 9. This coil or solenoidacts upon the iron core 14,which is carrid by a pivot-ed rocker-arm 15.The core 14 may be suitably subdivided in order to reduce eddy-currents,and for this purpose may be made of a bundle of fine wires,if sodesired. The returning movement for the core or rod 14 and the arm 15 issecured by means of the weight 16, adjustably mountedupon the lever-arm17, mechanically connected to the movingsystem already described. Apointer 18, movable over a scale, (not shown,) serves to indicate thequantity measured by the instrument.

' An additional coil 19 surrounds the coil 13, or is in any othersuitable manner arranged in inductive relation to the magnetic core 14.Through this coil or solenoid 19 an alternating current of suitablevalue and frequency is caused to pass. This alternating current may bederived from any suitable sourceas, for example, by means of acommutator or inverted rotary converter for changing direct current intoalternating current; or, on the other hand,the alternating current maybegenerated directly, as by the use of an alter- 8o nating-currentgenerator, (indicated in this case in the drawing at 20.) This generatoris shown as supplying current in series to the alternating-current coilsof two measuring instruments 21*and 22, as well as to the instrument 12of similar construction already described. This arrangement of circuits,however, is to be understood merely as illustrative, since it is obviousthat the mode of feeding the alternating current to therespeco tivemeasuring instruments may be carried out in a great number of differentWays with out departing from the spirit of my invention. A dotted line23 indicates an indefiniteextension of the closed series circuit fed bythe generator 20. i

The effect of the alternating magnetomotive force which is impresseduponthe iron cores of the measuring instruments described can beimagined to be to set the molecules of I00 the iron into rapidoscillation. During this oscillation the molecules are allowed intervalsof comparative freedom during which they readily yield to any externalmagnetomotive force that may exist. The resultant magnetization isthereby rendered free from the lagging elfect due to hysteresis, and theinstrument of which the magnetic core forms the propelling elementtherefore gives the same deflection upon a rising current as withfalling current. The amount of alternating magnetomotive force required,as well as the frequency of the same, depends upon the construction ofthe particular instrument to which my invention may be applied and mayreadily be found by trial. In the above eX- planation of my invention Ihave described the same as embodied in a simple form of currentmeasuringinstrument. It will be obvious, however, to those skilled in the artthat widely-diiterent applications of my invention may be made withoutdeparting from the spirit thereof. The invention may, for example, beapplied to voltmeters, wattmeters, and other measuring devices, as wellas to the ammeter or current-measuring device set forth. For a betterunderstanding of the scope of my invention attention is, however,directed to the claims appended hereto.

\Vhat I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. In an electric measuring instrument, the combination of relativelymovable members, and means for simultaneously impressing upon one of themembers a unidirectional magnetomotive force and an alternatingmagnetomotive force.

2. In an electric measuring instrument, the combination of a coil orwinding, a member of magnetic material within the in liuence of saidcoil or winding, an additional or auxiliary coil or winding, means forsupplying direct current to one of said coils or windings, and means forsupplying alternating current to the other coil or windin 3. In anelectric measuring instrument, the combination of a coil for carryingdirect current, an iron core, and means independent of said coil forimpressing upon said core an alternating magnetomotive force.

4. In an electric measuring instrument, the combination of a movablemember, and means for simultaneously impressing upon said movable membera unidirectional magnetomotive force and an alternating magnetomotiveforce.

5. In an electrical measuring instrument, the combination of adirect-current actuating-coil, a movable member, and means separate fromsaid member for impressing an alternating magnetomotive force on saidmovable member.

6. In an electric measuring instrument, the combination of adirect-current actuatingcoil, a movable member containing iron withinthe influence of said coil, an additional or auxiliary coil in operativerelation to said movable member, and separate sources of currentconnected respectively to said coils.

In witness whereof I have hereunto set my hand this 1st day of April,1901.

\VALTER G. FISH.

Witnesses:

DUGALD McK. MCKILLOP, JOHN A. MCMANUS.

